“The results of our study point to age-based licensing requirements as an effective way to improve safety,” said study co-author Steven Albert, of the University of Pittsburgh’s Graduate School of Public Health.

“But such requirements also may cause social isolation and depression, and may be seen as ageist and discriminatory,” said Albert, chair of behavioral and community health sciences.

Further study might determine the best approach to ensure safe driving without harming the mental health of older adults, he added in a university news release.

For this study, researchers analyzed 2004-09 data on nearly 137,000 older drivers in the United States who were hospitalized after a crash.

They found that hospitalized drivers, aged 60 to 69, in states with in-person license renewal laws were about 38 percent less likely to have dementia than those in states without such laws.

Also, in states with vision testing at license renewal, drivers were 23 to 28 percent less likely to have dementia than those in states without vision testing requirements, the study found.

Laws requiring doctors to report drivers with dementia were not linked with a lower chance of dementia among hospitalized older drivers, according to the study.

The findings were surprising “as we know that older drivers stop driving based on the advice of their physicians and, if reported to licensing authorities, few regain driving privileges,” said study lead author Yll Agimi.